Does it work on Apple iOS?

Android handles silent call log scanning natively. For iOS devices, users simply type in the last 4 digits of the caller ID.

Is the phone call free for the end user?

Yes. The call is disconnected prior to answering, resulting in zero charge for the recipient.

What is Bulk SMS's Voice API and how does it work in Brazil?

The Voice API allows companies to integrate automated phone calls and telephony workflows into their software. It operates over high-performance SIP connections with ANATEL-licensed telecom carriers.

What is the quality of the Text-to-Speech (TTS) engine used?

We utilize state-of-the-art AI-driven TTS engines. The Brazilian Portuguese pronunciation is fluid, respects punctuation pauses, and sounds like a friendly local customer representative.

How does the Dynamic IVR (URA) work in the Voice API?

You can program the voice flow to interact with the customer via DTMF keypress menus (e.g., "Press 1 for Billing, press 2 for Support") with key captures transmitted via webhooks in milliseconds.

Do you offer reliable Answering Machine Detection (AMD)?

Yes. Our advanced AMD algorithm sweeps the line in milliseconds during initial connection, differentiating active carrier mailboxes from live human responses, ensuring your message only plays upon human answer.

How is voice call pricing structured in Brazil?

Telephony rates follow ANATEL standard fractional billing (typically 30/6, meaning we charge a minimum of 30 seconds and then every 6 seconds), providing excellent cost optimization.

Does the Voice API support call recording and secure storage?

Yes. You can record calls automatically. The generated high-quality MP3/WAV audio files are stored in secure, encrypted buckets in Brazil, adhering to legal records guidelines.

What is the maximum simultaneous call capacity supported?

Our dedicated SIP trunk infrastructure scales from light business lines to high-throughput bursts of 50,000 concurrent calls for large enterprise notifications.

What is a Flash Call and how does it work?

A Flash Call is an alternative authentication method where the system places a quick 1-second call and hangs up before the user answers. The validation code is the last few digits of the caller ID.

Flash Call Verification API

What is Flash Call verification?

Flash Call triggers an automated short call to the user’s mobile. The SDK on the user’s phone reads the last digits of the incoming calling number to authenticate the session.

Because the call is dropped before being answered, there are no minute connection charges, making it highly efficient.

Flash Call Metrics

Average Verify Latency:< 3.5s

Budget Savings vs SMS:Up to 60%

Android Validation Rate:96.2%

Flash Call Key Benefits

Seamless Verification

No manual code input required for Android users; verification happens silently.

Dramatically Lower Costs

Saves telecom budget compared to outbound SMS text delivery.

Rapid Verification Loop

Confirms active mobile network presence in under 4 seconds.

Technical Integration

Step-by-Step Implementation

01

SIP Trunking or Voice API Provisioning

Provision cloud telephone lines or connect your on-premise PBX servers straight to our local carrier nodes.

02

Script Authoring & TTS Config

Pre-record custom voice audio files or configure the neural Text-to-Speech (TTS) speech engine to read dynamic user parameters.

03

Operations & CDR Monitoring

Track call completion parameters, query detailed CDR call records, and access secure recordings.

Practical Use Cases

Industry-Specific Solutions

Banking & Fintech

Automated high-value Pix checks, dynamic phone confirmations, secure token deliveries, and voice 2FA fallbacks.

Varejo & E-commerce

Post-delivery NPS calling, automated user feedback collection via dial keypad values (DTMF), and sales confirmation.

Healthcare & Clinics

Urgent clinic schedule updates, automated reminders for elderly patients, and secure appointment rescheduling.

Logistics & Shipping

Pre-flight recipient checks, automated phone confirmation before dispatch, and logistics problem notifications.

Why Choose BulkSMS?

Carrier-Grade Local Telecommunications

Unlike legacy global aggregators that rely on unreliable third-party transit paths, BulkSMS owns carrier-grade direct pipelines with Vivo, Claro, TIM, and Oi.

We host our physical core architecture in São Paulo datacenters. This keeps voice compliance fully aligned with Brazilian data security standards (LGPD) for all auditing requirements.

Our engineering operations desk provides qualified support in Portuguese 24/7/365, giving your product and dev teams immediate developer-to-developer assistance.

Direct SIP Trunks

IP voice trunking with excellent codecs.

LGPD Sovereignty

São Paulo datacenters protecting user data.

24/7 Portuguese Support

Talk directly to local telecom developers.

99.9% Outbound SLA

Contractual uptime for critical transaction paths.

Real Customer Stories

What our customers say
about our services

"The Brazilian Portuguese Text-to-Speech (TTS) voice quality is impressive. It sounds extremely natural."

HM

Humberto Martins

Rio de Janeiro - RJ

"Our automated collections center now places 50,000 simultaneous calls with excellent SIP trunk stability."

VP

Vivianne Pasmanter

Minas Gerais - MG

"The Voice API allowed us to build a dynamic IVR flow integrated in real-time with our database."

MP

Marcos Pasquim

São Paulo - SP

"Excellent documentation for dedicated SIP trunking configuration. Fast activation and responsive team."

PF

Priscila Fantin

Santa Catarina - SC

"We use the predictive dialer hooked into Bulk SMS's Voice API, and our sales productivity jumped 35%."

MS

Malvino Salvador

Goiás - GO

"Answering Machine Detection (AMD) that actually works reliably in the Brazilian mobile telecom landscape."

FA

Flávia Alessandra

Rio de Janeiro - RJ

"Call recordings and detailed logs (CDRs) integrate natively with our secure AWS buckets under encryption."

CC

Caco Ciocler

São Paulo - SP

"A robust telephony platform that handles transactional voice flows and DTMF menus perfectly."

LS

Letícia Spiller

Santa Catarina - SC

Resources & Insights

Flash Call FAQ

99.9% SLA · 24/7 Support · LGPD Compliant

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Operational Use Cases

Brazil Infrastructure

Flash Call — Low-Cost Missed Call Authentication